1. Field of the Invention
The present invention relates to rotary switches utilized for the selection of different modes of operation in ranges, ovens, etc. Particularly it pertains to a method of determining on a low voltage basis the position of the switching mechanism.
2. Background Art
Electric ranges and similar devices typically have control devices for the apparatus which allow the operator to select the mode in which the device is to be used. For example, in an oven, seven positions of the rotary selector switch might include off, convection baking, baking, cleaning, conventional cooking, broiling and convection broiling. In the usual arrangement, a rotary switch provides the necessary selection. Control effected by such a rotary switch provides the necessary electro-mechanical controls which operate on 120 VAC and 240 VAC. In today's technology where microcomputers and similar units are utilized for control, low voltage DC is typically used for control information. Accordingly, it is quite desirable to provide a low voltage indication of the position (or selection) to which the rotary switch has been operated to provide an indication to the control equipment of that position and the function to be controlled.
Devices which have been utilized for this particular purpose which might be applied included such as those disclosed in U.S. Pat. No. 4,580,138 which disclose a measurement expressing apparatus including a plurality of electrical switches with a separate different resistance associated for each step with the resistances being binary related value to each other. The resultant analog to digital output is in N-bit binary weighted form. A potentiometer having a switching function which might be employed in a similar environment is taught by U.S. Pat. No. 4,647,897. It utilizes a three wire potentiometer with an on-off switch at one end with three wires running on three concentric tracks.
Yet another approach is taught in U.S. Pat. No. 4,740,672 which provides a binary output signal with a dual output. when rotated, the unit disclosed generates a first and second pulse train. Another oven controller which attacks some of the same problems provides several independent switches without resistors is shown in U.S. Pat. No. 4,849,597. The arrangement thus provides a digital output rather than analog as taught by the present invention. Each switch accordingly requires its own wire lead and provides a binary coded device.
As electronic controls interface with electro-mechanical controls a method of communicating between the two controls is required. Since electro-mechanical controls typically operate on 120 VAC and electronic controls use a low voltage DC, a communication link involves isolating the voltages and reducing the AC voltage to a DC equivalent voltage. This typically requires many components and is very expensive. None of the elements as known in the prior art as described above provide a simple economical means for dealing with that particular problem. Accordingly, it is the object of the present invention to provide a new and economical efficient method of determining the position of a rotary switch on a two wire low voltage basis.